1. Field of the Invention
The present invention relates to a boot or seal for a power transmitting mechanical joint of the plunging type, especially for a joint which is subject to articulation during operation. More particularly, this invention relates to a boot or seal of the aforesaid type in which at least a portion of such boot is of a non-flexible character. Specifically, this invention relates to a boot or seal for a constant velocity joint of the type used as the inboard drive joint in an arrangement for driving a front wheel of a front wheel drive automotive vehicle, in which the portion of the seal or boot which engages the outer race of the joint is of a semi-rigid character.
2. Description of the Prior Art
Plunging constant velocity drive joints are widely used in the automotive industry as means to transmit power from the transmission of a front wheel drive vehicle to the driven front wheels of the vehicle, with one of such joints being provided for each of the driven wheels. Typically, a plunging drive joint is used as the inboard or inside drive joint in an arrangement where another drive joint of the non-plunging joint is used as the outboard or outside drive joint, and all changes in the spacing between the transmission and the driven wheel are accommodated by the plunging action of the input and output members of the plunging joint with respect to one another. Each such drive joint must be sealed, of course, to maintain the necessary lubrication in place within the joint and to keep the joint free from contamination by dirt and other external contaminants.
In the case of mechanical joints of the plunging type, the devices heretofore used to accomplish this sealing function, which are usually referred to as seals or boots, have been of a flexible construction, usually constructed of an elastomeric material and usually in a pleated configuration. Such flexible construction, however derived, gives the boot the ability to distort to accommodate both articulation or angular movement of the normally axially aligned input and output members of the joint, an operation condition which can develop due to road vibration or cornering, for example, as well as lineal or axial movement between the input and output shafts, a condition which can occur even when the engine is idling due to the tilt of the engine which results therefrom, without breaking the seal of the joint during such articulation and/or lineal or axial movement.
Flexible boots or seals for plunging automotive constant velocity drive joints, as heretofore described, have been utilized quite extensively. However, these seals are quite expensive, and due to the fact that their dimensions readily change by virtue of their flexible nature, they must be installed using manual operations, which precludes the use of some cost-saving mechanical assembly techniques that rely on precise dimensions of the parts being installed. Additionally, these flexible boots or seals, which are made from elastomeric materials, are subject to puncture in use due to road hazards and other forms of concentrated impacts, and these materials are known to be subject to degradation of properties when exposed to low temperatures or high temperatures of the type that can be encountered during the normal life of an automobile. Additionally, due to the pleated configuration of these flexible boots or seals, the interior volume thereof is rather large and this volume, which must be filled with grease to properly lubricate the associated joint, requires a rather large volume of grease for that purpose. Furthermore, many elastomeric materials are subject to degradation when exposed to grease, and this grease sensitivity further limits the useful life of such flexible seals.